Field of the Invention
The present invention relates to a method for preparing a sintered zirconia body in sheet form having length, width and thickness dimensions characterized by a high surface area to thickness ratio and a high length to thickness ratio.
Sheets of sintered zirconia body were prepared by various well-known methods including doctor blade, calender roll and extrusion methods. The doctor blade method involves dispersing zirconia powder in an organic binder and a solvent, applying the resulting slurry onto a carrier tape to a uniform thickness by means of a doctor blade, drying to evaporate off the solvent, and solidifying into a green sheet. The green sheet is then cut, punched or otherwise worked and fired into a sintered sheet.
The thus obtained sheet form of sintered body is liable to camber or become wavy as its thickness is reduced, particularly when green sheets prepared from submicron zirconia particles are fired. Where sintered sheets have a practically unacceptable extent of camber or waviness, such camber or waviness must be compensated for, for example, by re-firing the sheet under a preselected load. However, two or more steps of firing are undesirable from the aspect of energy saving. Also, application of a load to cambered or wavy sintered sheets can cause cracking and breakage of the sheets, resulting in low manufacture yields. Additionally, as the surface area to thickness ratio or length to thickness ratio of sheets increases, the influence of camber or waviness during firing is enhanced, to resulting in more frequent occurrence of cracking or breakage.